Despite the advances made in technologies such as medical imaging to assist the physician in early stage diagnosis and treatment of patients with possible atypical tissue such as cancer, it is still often necessary to sample difficult-to-reliably-reach organ or tissue lesions by biopsy to confirm the presence or absence of abnormalities or disease.
One disease for which biopsy is a critical tool is breast cancer. This affliction is responsible for 18% of all cancer deaths in women and is the leading cause of death among women aged 40 to 55.
In the detection and treatment of breast cancer, there are two general classes of biopsy: the minimally invasive percutaneous biopsy and the more invasive surgical, or “open”, biopsy.
Percutaneous biopsies include the use of fine needles or larger diameter core needles. They may be used on palpable lesions or under stereotactic x-ray, ultrasonic, or other guidance techniques for nonpalpable lesions and microcalcifications (which are often precursors to metastatic cell growth). In the fine needle biopsy, a physician inserts a small needle directly into the lesion and obtains a few cells with a syringe. Not only does this technique require multiple samples, but each sample is difficult for the cytologist to analyze as the specimen cells are isolated outside the context of healthy surrounding tissue.
Larger samples may be removed via a core biopsy. This class of procedures is typically performed under stereotactic x-ray guidance in which a needle is inserted into the tissue to drill a core that is removed via vacuum aspiration, etc. Typically four to five samples are taken from the body. Examples of such stereotactic biopsy methods include the MAMMOTOME vacuum aspiration system by Johnson & Johnson of New Brunswick, N.J., the ABBI system by United States Surgical Corporation, Norwalk, Conn., and the SITESELECT system by Imagyn, Inc. of Irvine, Calif.
Open biopsies are advisable when suspicious lumps should be removed in their entirety or when core needle biopsies do not render sufficient information about the nature of the lesion. One such type of open biopsy is the wire localization biopsy.
After multiple mammograms are taken of the breast, the images are analyzed by a computer to determine the location of the suspect lesion in three dimensions. Next, after a local anesthetic is administered, a radiologist inserts a small needle into the breast and passes the needle through the suspect tissue. The radiologist then passes a wire with a hook on its end through the needle and positions the hook so that the end of the wire is distal to the suspect tissue. A final image is taken of the lesion with the accompanying wire in place, and the radiologist marks the film with a grease pencil to indicate the x-ray indicators of a suspicious lesion that should be removed. The wire is left in the tissue and the patient is taken to the operating room, sometimes hours later, where the suspect tissue is removed by a surgeon. The sample is sent to a radiologist to determine, via an x-ray examination, if the sample contains the indicators such as microcalcifications and if the sample size and border are adequate to confirm the removal of all suspicious tissue.
Examples of such wire markers are well known in the art. See, e.g., the following patents, each of which is incorporated herein by reference: U.S. Pat. No. 5,158,084 to Ghiatas, U.S. Pat. No. 5,409,004 to Sloan, U.S. Pat. No. 5,059,197 to Urie et al., U.S. Pat. No. 5,197,482 to Rank, U.S. Pat. No. 5,221,269 to Miller et al., and U.S. Pat. No. 4,592,356 to Gutierrez. Other devices such as that described in U.S. Pat. No. 5,989,265 to Bouquet De La Joliniere et al. and U.S. Pat. No. 5,709,697 to Ratcliff et al., each incorporated herein by reference, are directed to similar devices.
Despite the advantages of wire focalization techniques to locate the suspect tissue for the surgeon, they have a number of severe limitations.
Such wires are often inaccurately placed and they cannot be removed except by surgical excision. For these reasons, the radiologist must mark the x-ray film or prepare notations providing instructions to the surgeon on how to find the lesion as a backup to confirm the proper location of the needle.
Because the distal tip of the wire might have been placed anywhere from the very center of the lesion to quite some distance away from the lesion, the surgeon must guide a scalpel along the wire and rely upon the skill of the radiologist and the marked x-ray film in the excision procedure. Even if the wire has been properly placed in the lesion and the x-ray film clearly shows the lesion boundary or margin, the surgeon often cannot see the tip of the wire (given the surrounding tissue) so she must remove a larger portion of tissue than is necessary to ensure proper excision.
If the lesion is not found at the end of the wire, the surgeon ends up cutting or removing non-afflicted tissue without removing the lesion. Also, if the tip of the wire penetrates the lesion, the surgeon may sever the lesion in cutting through the tissue along the wire to reach its end. In the latter case, a re-excision may be necessary to remove the entire lesion. Over twenty-five percent of wire localization procedures require re-excision. Post-excision re-imaging is almost always performed prior to closing the surgical field to ensure that the targeted tissue volume containing the suspect lesion is removed.
When marking lesions in the breast, two paddles are typically used to compress and stabilize the breast for placement of the wire. Upon release of the breast from compression, the wire marker can dislodge or migrate to another position away from the suspect tissue. It may also migrate while the patient awaits surgery. In addition, the fact that the breast is in an uncompressed state for the excision procedure renders a different view of the lesion with respect to the healthy tissue.
Various tissue localization systems have been developed to minimize inadvertent migration of the wire by configuring the wire with a bend or hook, such as Ghiatas et al., discussed above, U.S. Pat. No. 5,011,473 to Gatturna, and the MAMMALOK needle/wire localizer sold by Mitek Surgical Products, Inc., Dedham, Mass. Even if a wire does not migrate after placement, the surgeon cannot determine the shortest path to the lesion; rather, the surgeon must always follow the wire, which is rarely the more cosmetically desirable path to the lesion (such as a circumareolar approach).
Because the distal tip of the wire is often placed in the center of the suspect tissue, a problem known as “track seeding” can occur in which possible cancerous or precancerous cells are disturbed by the wire and are distributed to unaffected tissue during the procedure.
Aside from the above concerns, the use of a localization wire marker presents logistical problems. After placement, the wire protrudes from the body. It is almost always necessary for the patient to proceed with the surgical removal of the lesion immediately after wire placement to minimize the chance of infection, wire breakage or disturbance, etc. However, delays between placement of the wire and eventual excision often can exceed several hours.
Furthermore, conventional tissue locators tend to be difficult to deploy in areas where there is scar tissue, calcified tissues, or particularly dense tissues. The locator element or wiring that is inserted into the tissue tends to be blocked by scar tissue and other hardened tissues. It is highly desirable to have an effective means to facilitate the insertion of a locator element by minimizing resistance due to calcified tissue and other hardened tissues.
What is needed is a tissue-locating device that may be smoothly inserted into the subject to surround a volume of interested tissue with minimal effort and maximum precision. Such a device should reliably define the border of the volume of tissue to be removed without the risk of self or inadvertent migration. The device should also provide a surface against which the surgeon may reliably cut when excising the tissue. Furthermore, a need remains to improve the interaction between the radiologist and surgeon, eliminate the need for post-excision x-rays and re-excision, reduce the overall time for the procedure, and allow a surgeon to select the shortest or most cosmetically desirable path to the suspect tissue.